An eco-friendly protocol for the biosynthesis of extracellular zinc nanoparticles (ZnNPs) by Penicillium chrysogenum was performed. The formation of ZnNPs was observed by the formation of white aggregates of ZnNPs and confirmed by UV absorption spectrum at 340nm. The synthesized ZnNPs were also characterized by High resolution transmission electron microscope (HR-TEM), dynamic light scattering (DLS) and fourier
transform infrared spectroscopy (FT-IR). The optimum conditions were pH 10, 72h of reaction between culture filtrate (CF) and 1mM (ZnSO4) solution with (6:1) ratio. Exposure of ZnNPs to gamma radiation showed an increase in the absorption band intensities when compared to the non irradiated sample. Samples of ZnNPs exposed to 20kGy dose recorded the greatest antimicrobial effect. The study of its antitumor activity against human breast carcinoma (MCF-7) and colon carcinoma cells (HCT-116) was performed. The IC50 values of (MCF-7) were 373μg/ml and >500μg/ml, while of (HCT-116) were 226 and 317μg/ml for irradiated
and non irradiated samples, respectively. TEM and DLS showed the formation of spherical monodispersed ZnNPs from 9 to 17nm with a mean of 13nm for the irradiated sample exposed to 20kGy. The current research provided an insight on using ɤ-radiation as a highly efficient and inexpensive tool for the enhancement of antimicrobial and antitumor effects of nanoparticles against infectious and tumor diseases.